Television receiving apparatus



Nov. 7, 1939. P.'M. 3.y TOULON 2,179,205

TELEVI S'I 0N RECEIVING -PPARTUS Filed Jan.` 25. 1957 Patented Nov. 7, 1939 .PATENT `ori-ica 2,119,205 TELEVISION alici-:WING APPARATUS Pierre Marie Gabriel Toulon,

Application January 25,

Claims.

According tothe known methods of electrical transmission of moving images, in order to ensure the continuity of visual impression, a certain number of images is transmitted per second;

5 each image is formed of a certain number of lines and each line is constituted by a certain number of points (image elements).

point there corresponds an electrical impulse of a certain amplitude. In the receiving set, this electricall impulse is transformed into a luminous poin` the brilliancy of which varies in accordance with its amplitude; this point constitutes one element of the image received. As transformers of the current into light, a l5 Braun tube is most frequently employed at the present day, in which the luminous point is produced by an electronic beam modulated by the electrical impulse and impinging on a screen. The vuse of luminous discharge tubes,

Kerr cells etc. is also known, all these devices transforming the current received into modulated light and usually being combined with mechanipal scanning devices, such as .Nipkow discs, Weiler drums, etc.

In all present day television receivers, this transformation of the current into' light is done in an instantaneous manner and, the duration of the luminous phenomenon is equal to the duration of the electrical impulse. The present invention has for its object a new method of reception which is characterised by the feature that the duration of the luminous impulse exceeds that of the electric current.

While all present-day receivers are characterised by the direct transformation of the current impulse into a luminous point,` according to the present invention there is introduced into the receiver an additional member which is subjected to the action of the electrical impulses and which serves in turn to vary the intensity of the luminous point. This member is arranged and operated in such a. manner that it undergoes, under the influence of an electrical impulse, a modication which is a function of the impulse, and

this modification is maintained for an interval of time which is longer than the duration of the impulse. Preferably, the arrangements are such that this interval is substantially equal to the time of scanning of the entire image. According 5o to the invention, and due to this collecting member, the result is obtained that the luminous points will maintain their brilliancy for an interlval of time which is much longer than in known receivers. If, for example, the image were con- 55 stituted by 100,000 points, and, if according to To each image be suitable for projection onto ascreen. Y

fluorescent Puteaux, Franci 1937, Serial No. 122,275

In France January 30, 1936 (Cl. TIS- 7.5)

the invention, the brilliancy of a point were maintained throughout the transmission of an image, each point would make an impression on theeye of the observer for a time which is 100,000 times longer than in existing receivers. The 5 image` obtained accordlng to the invention will therefore be much more brilliant and will even Applied to receivers employingv a cathode beam and uorescent screen, the invention, without 10 sacrificing the luminosity, allows of working with an electronic beam which is relatively little powerful and little accelerated, while in existing Braun tube receivers, it is necessary, in order to ensure a sufficiently luminous image, to bombard l5 the fluorescent screen violently, which deteriorates it and reduces the life of the tube. Attempts have been made in these tubes to increase the optical effect by employing a uorescent su stance having a certain luminous inertia, but 2o this veffect necessitates a more intense bombardment of the screen, which is therefore even more detrimental tothe lift of the tubesi moreover, this property is diiiicult to adjust and to maintain constant.

The second feature oi the operation of a receiver according to the invention, that is, the control of the intensity of the luminous points by the collector. may have for result either that the point remains luminous throughoutthe in- 30 terval of time elapsing between the transmission of two successive images (arrangements may be made vso that its brilliancy Aremains constant during the whole of this time; in certain cases it may vary progressively).

The invention also offers the advantage of the diminution and even suppression of the flickering effect of the image received. Owing to a cer tain continuity in the luminosity of the points of the image, it is even possible, without interfering 40 with the optical eiciency and without introducing the phenomenon of flickering, to reduce the number of images transmitted per second and, therefore, to diminish the frequency band for transmission.

The accumulation or, more exactly, the storage of the electrical image impulses on the collecting device may be done in the form of an electric charge (for example, an electronic deposit).

After the accumulation of the electrical impulses on the collector and their transformation into luminous points, the collector is restored to its original state so as to be able to accumulate there the impulses of the following image. This method of clearing may be either instantaneous (that is, the charge o1' the collector corresponding topan impulse will be suddenly effaced) or progressive. The instantaneousclearing is preferably eifected by the scanning o! the collector syn' chronously with the accumulation of the electrical impulses. The progressive clearing may be effected, for example, by the charge owing away in a conductor oilering a. certain resistance.

charged one after the other image impulses and their charges are transformed into luminous points.

According to a modification of the invention, in the case where it is applied to receivers employing a cathode beam and fluorescent screen, use is preferably made of such a collector comprising multiple elements or cells, and the latterY are successively charged by an electronic beam i modulated by the electrical image impulses and and the second gun 22 utilising these electrified charges for producing locally the luminosity of the screen 2l.

In this gure, 9

the scanning of the surface of the electrode l2. which constitutes a collector. The scanning system is synchronized,

as is customary, from the image redevice 8, which receives not only the modulation but also the synchronising signals.

Contrary to the televisionv receiving devices comprising a Braun tube as have been employed up to the present day, the electrode I2 is not covered with fluorescent material anddoes not serve but serves'only for the in- It is possible to employ the charges so deposited cally on the collector for controlling the luminosity of the fluorescent screen 2|.

To this end, the different ing electrode I2 of the charges deposited owing to the the contrary, gun 22 is controlled from the point of intensity, at each of the points of its passage across the intervals between the slats collecting electrode l2, so that the fluorescent screen 2l, which receives the electrons of the Fig, 2 which reproduces, on an enlarged scale, the details of execution of the collecting electrode I2 of Fig. 1 clearly shows how the control of the ux of the second electron gun 22 is I2) and from the gun 22 (causing the illumination of the screen 2|)' As can be seen in this figure, the constitution of the support 24, 25, 26 is such that the insulating plates are carefully protected against an electron flux proceeding from the gun 22. Thus the front edges of the support 24, 25, 26 may be anged so as to extend upwardly slightly above the surfaces of-.the insulating plates, as shown. If necessary, an auxiliary grid 20 is used in addition for increasing this eiect. The process of modulation of the beam of the gun 22 by the charges I6, I1, I8 is electrostatic. deposited at points such as I1, the potential of this surface is the same as that of the opposite conductive lsupport 24. The electrons of the gun 22 are not deflected from their path and the fluorescent screen 2| appears luminous throughout the distance which separates two consecutive bands, that is, at 29-30. The dimensions of the luminous point so obtained are large enough. On the contrary, if charges have been deposited at points such as |'I (or I6, I8 etc.), the second beam proceeding' 3|, 33. Part of the electrons is absorbed by the conductor 24. The surface 'of the fluorescent screen 2| impinged upon is reduced at 3|, 32. This reduction of the dimensions of the point (therefore of the local luminous intensity) is as much more accentuated as the charge deposited upon the insulating support has been more increased. The second electron flux (gun 22) may be very intense, as this gun need not furnish, likethe spot of the gun 6, a very concentrated iiux; this flux is, on the` contrary, uniformly distributed over the whole of the surface of the screen, and the mutual repulsion of the electrons is therefore without disadvantage. This flux is no longer concentrated on one of the successive points, as is generally done in Braun tubes employed at the present day in television; therefore, there is no risk of causing the deterioration of the phosphorescent material, while maintaining an extremely intense mean luminosity which allows the projection of an image onto a large-size screen. It is interesting to note that the gun 6 may have a very low power, as small charges are sufficient for effecting the control of the second beam. The electron gun 22, which produces the luminosity of the screen 2| Vmay operate continuously. In the example described, the charges deposited atpoints such as I6, I'I, I8 disappear progressively as a result of the imperfect insulation of the support. However, it may be advantageous to obtain the sudden discharge, immediately before the passage of the exploring beam. To obtain this sudden discharge, the means may be employed. The insulating surface is covered with a material capable of emitting secondary electrons (for example, nickel). A second scanning electronic beam is employed, which is moved in synchronism with the first but displaced with respect thereto. The electrons of this second beam are moved at a very high initial speed. By implnging upon the surface of the collector I2, the secondary electrons so released cause the charge deposited by the beamv 6 modulated by the signal to disappear.

The discharge may also be effected by means of a luminous or ultra-violet beam, the surface of the collector being covered with a photo-emissive substance.

I claim:

l. Receiving tube comprising a uorescent screen, a first electron gun emitting a rst elec- In the absence of electric charges from the gun 22 is d eected at v substantial width lying in following tronic beam, a second electron gun emitting a second electronic beam, a multi-cellular collecting grid arranged between said fluorescent screen and said rst and second electron guns, said collecting grid including a series of slats of substantial width compared with the distance between them, said slots lying in planes inclined to the path of the electrons emanating from said first electron gun so as to obstruct the passage of said electrons and substantially parallel to the path of the electrons emanating from said second electron gun so as to provide a substantially unobstructedpassage for said electrons, each of said slats comprising bands of insulating material forming the surfaces ofthe slats exposed to the electrons emitted by said first` electron gun and bands of conductive material form'- ing the under surface of said slats, means asso- Y ciated with one of said electron guns for concentra'tingl the beam emitted by said electron gun and for causing it to scan said collecting grid to deposit charges on said bands cf insulating ymateriaL means associated with the other electron gun for spreading the electronic rays emitted by said gun over the area of said collecting grid, whereby the rays of said second electron beam, in passing between said insulating slats are deiiected to an extent dependent upon the charges on the parts of the strips by which they pass, and by striking the bands of conductive material are absorbed in a number dependent upon their deflection.

2. Receiving tube comprising afluorescent screen, a rst electron gun emitting a rst electronic beam, a second electron gun emitting a second electronic beam, a collecting grid arranged between said fluorescent screen and said first and second electron guns, said collecting grid comprising a series of supporting stripsof planes inclined to the path of the electrons emanating from said first electron gun and substantially parallel to the path of the electrons emanating from said second electron gun and charge receiving cells mounted on said strips, each cell corresponding to a picture point, means associated with one of said electron guns for concentrating the beam emitted by said electron gun and for causing it to scan said collecting grid to deposit charges on each of said cells, means associated with the other electron gun for spreading the electronic rays emitted by said gun over the area of said collecting grid, whereby the rays of the second electron beam passing between said strips are deflected to an extent dependent upon the charges on the cells by which they pass and, by striking the strips towards the rearward edges thereof, are adsorbed in a number dependent upon their deection.

3. Receiving tube comprising a fluorescent screen, a first electron gun emitting a first electronicbeam, a second electron gun emitting a second electronic beam, a collecting grid arranged between said fluorescent screen and said first and second electron guns, said collecting grid comprising a series of supporting strips of substantial width lying in planes inclined to the path of the electrons emanating from said first electron gun and substantially parallel to the path of the electrons emanating from said second electron gun and charge receiving cells mounted on said strips, each cell corresponding to a picture point, means associated with one of said electron guns for concentrating the beam emitted by said electron gun and for causing it passing between said strips are deiiected to an l 1o extent'dependent upon the charges on the cells by which they pass and, by striking the strips towards the rearward edges thereof, are adsorbed in a number dependent upon their deiiection.

4. Receiving tube comprising a uorescent screen, a first electron gun emitting a irst electronic beam, a second electron gun emitting a second electronic beam, a collecting grid arranged between said fluorescent screen and said first and second electron guns, said collecting grid comprising a series of supporting strips of substantial width lying in planes inclinedto the path of the electrons emanating from said rst electron gun and substantiallyparallel to the path of the electrons emanating from said scc- 25 ond electron gun and charge receiving cells mounted on said strips, each cell corresponding to a picture point, means associated with one of said electron gunsfor concentrating the beam emitted by said electron gun and for causing it 30 to scan said collecting grid to deposit charges on each of said cells, means associated with the other electron gun for spreading the electronic rays emitted by said gun over the area of said collecting grid, the edges of the supporting strips facing the electron guns, being turned upwardly slightly above the charge receiving surfaces of the cells to protect said cells from the electrons emitted by said second electron gun, whereby the rays of the second electron beam passing between said strips are deected to an extent dependent upon the charges on thecells by which they pass and, by strlkingthe strips towards the rearward edges thereof, are adsorbed in a number dependent upon their deection.

5. Receiving tube comprising a uorescent screen, a first-electron gun emitting a first electronic beam, a second electron gun emitting a second electronic beam, a collecting grid arranged between said fluorescent screen and said Ilrst and second electron guns, said 'collecting grid comprising a series of supporting strips of substantial width lying in planes inclined to the path of the electrons emanating from said iirst electron l gun and substantially parallel to the path of the electrons emanating from said second electron gun and charge receiving cells 'mounted on said strips, each cell corresponding to a picture point, means associated with one of said electr@1 guns for concentrating the beam emitted by said electron gun and for causing it to scan said collecting grid to deposit charges on each of said cells'. means associated with the other electron gun for spreading the electronic rays emitted by said 2 gun over the area of said collecting grid, whereby the rays of the second electron beam passing between said strips are deflected to an extent dependent upon the charges on the cells by which they pass and, by striking the strips towards 31 the rearward edges thereof, are adsorbed in a number dependent upon their deiiection, said cells and said supporting strips having suilicient conductivity to form a leakage resistance permitting the charges to leak away between each successive 3c scanning operation.

PIERRE MARIE GABRIEL TOULON. 

